1. Field of the Invention
The invention relates to an arrangement of inductive voltage transformers for installation in a completely insulated high-voltage switching installation comprising a metal encapsulation and several high-voltage conductors.
2. Description of the Prior Art
The manufacture of inductive voltage transformers for completely insulated high-voltage switching installations of the above-type presents no significant difficulties regarding compliance with technical requirements related to voltage measurments. However, problems do arise due to the insulation required and, in particular, due to the available space for housing the transformers, which is determined by the dimensions of the measuring capsule. Heretofore such space problems could not be adequately solved, so that only arrangements employing capacitive voltage transformers have been used to date in encapsulated high-voltage switching installations.
The capacitive voltage transformers in the aforesaid known arrangements always contain a capacitive voltage divider followed by an amplifier. The capacitive voltage divider comprises a high-potential capacitor, which includes a respective high-voltage conductor of the switching installation as one of its electrodes and a measuring electrode of large area, arranged at a distance from the high-voltage conductor, as the other of its electrode. Additionally, the voltage-divider comprises a low-potential capacitor, the latter being formed by a further, large-area electrode arranged at a distance from the measuring electrode or by a separately arranged capacitor connected to the measuring electrode.
The space problems encountered with capacitive voltage dividers or transformers can be solved without difficulty, as such transformers require only relatively thin area electrodes to be disposed in the radial direction and further require only a thin insulating layer to insulate the electrodes from the grounded metal encapsulation. However, to provide power analogous to that delivered at the secondary of an inductive voltage transformer, such capacitive voltage transformers must be followed by an amplifier, for which a supply voltage source must also be provided.
It is an object of the present invention to provide an arrangement comprised of inductive voltage transformers which can be installed in a cylindrical portion of a metal capsule of a completely insulated high-voltage switching installation without enlarging the metal capsule in the radial direction.